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    Subject[RFC PATCH v2, part3 05/11] PCI: enhance PCI core logic to support PCI bus lock
    Date
    Every new PCI bus will be created with the PCI_BUS_STATE_LOCK bit set,
    so a typical PCI device hot-add flow is:
    pci_bus_lock(parent, PCI_BUS_STATE_STARTED, true);
    pci_scan_slot(parent, PCI_DEVFN(0, 0));
    pci_bus_add_devices(parent);
    pci_bus_unlock(parent, true); // recursively unlock all PCI
    // buses, including new PCI buses

    This patch also changes behaviors of interfaces to create PCI root buses:
    pci_create_root_bus(): return with new PCI root bus locked
    pci_scan_bus_parented(): return with new PCI root bus locked
    pci_scan_root_bus(): return with new PCI root bus unlocked
    pci_scan_bus(): return with new PCI root bus unlocked

    pci_scan_bus_parented() has already been marked as __deprecated and
    all in-tree callers have been converted to use other interfaces.
    So following-on patches will enhance callers of pci_create_root_bus()
    to unlock returned root buses.

    Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
    Cc: Yinghai Lu <yinghai@kernel.org>
    Cc: linux-pci@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    ---
    drivers/pci/hotplug-pci.c | 4 ++++
    drivers/pci/probe.c | 18 ++++++++++++++++++
    2 files changed, 22 insertions(+)

    diff --git a/drivers/pci/hotplug-pci.c b/drivers/pci/hotplug-pci.c
    index 18533ed..8faa3c2 100644
    --- a/drivers/pci/hotplug-pci.c
    +++ b/drivers/pci/hotplug-pci.c
    @@ -10,6 +10,10 @@ int __ref pci_hp_add_bridge(struct pci_dev *dev)
    int pass, busnr, start = parent->busn_res.start;
    int end = parent->busn_res.end;

    + BUG_ON(!pci_bus_is_locked(parent));
    + if (pci_bus_get_state(parent) > PCI_BUS_STATE_STARTED)
    + return 0;
    +
    for (busnr = start; busnr <= end; busnr++) {
    if (!pci_bus_exists(pci_domain_nr(parent), busnr))
    break;
    diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
    index 9fcf3a3..0ddf5b8 100644
    --- a/drivers/pci/probe.c
    +++ b/drivers/pci/probe.c
    @@ -745,6 +745,10 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
    u8 primary, secondary, subordinate;
    int broken = 0;

    + BUG_ON(!pci_bus_is_locked(bus));
    + if (pci_bus_get_state(bus) > PCI_BUS_STATE_STARTED)
    + return max;
    +
    pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);
    primary = buses & 0xFF;
    secondary = (buses >> 8) & 0xFF;
    @@ -799,6 +803,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
    pci_bus_insert_busn_res(child, secondary, subordinate);
    child->bridge_ctl = bctl;
    pci_bus_get(child);
    + } else {
    + BUG_ON(!pci_bus_is_locked(child));
    }

    cmax = pci_scan_child_bus(child);
    @@ -837,6 +843,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
    goto out;
    pci_bus_insert_busn_res(child, max, 0xff);
    pci_bus_get(child);
    + } else {
    + BUG_ON(!pci_bus_is_locked(child));
    }
    buses = (buses & 0xff000000)
    | ((unsigned int)(child->primary) << 0)
    @@ -1322,6 +1330,7 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
    {
    int ret;

    + BUG_ON(!pci_bus_is_locked(bus));
    device_initialize(&dev->dev);
    dev->dev.release = pci_release_dev;

    @@ -1369,6 +1378,10 @@ struct pci_dev *__ref pci_scan_single_device(struct pci_bus *bus, int devfn)
    {
    struct pci_dev *dev;

    + BUG_ON(!pci_bus_is_locked(bus));
    + if (pci_bus_get_state(bus) > PCI_BUS_STATE_STARTED)
    + return NULL;
    +
    dev = pci_get_slot(bus, devfn);
    if (dev) {
    pci_dev_put(dev);
    @@ -1624,6 +1637,8 @@ unsigned int pci_scan_child_bus(struct pci_bus *bus)
    unsigned int devfn, pass, max = bus->busn_res.start;
    struct pci_dev *dev;

    + BUG_ON(!pci_bus_is_locked(bus));
    + BUG_ON(pci_bus_get_state(bus) > PCI_BUS_STATE_STARTED);
    dev_dbg(&bus->dev, "scanning bus\n");

    /* Go find them, Rover! */
    @@ -1872,6 +1887,8 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
    pci_bus_update_busn_res_end(b, max);

    pci_bus_add_devices(b);
    + pci_bus_unlock(b, true);
    +
    return b;
    }
    EXPORT_SYMBOL(pci_scan_root_bus);
    @@ -1908,6 +1925,7 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
    if (b) {
    pci_scan_child_bus(b);
    pci_bus_add_devices(b);
    + pci_bus_unlock(b, true);
    } else {
    pci_free_resource_list(&resources);
    }
    --
    1.8.1.2


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